Transport of particulate solids, such as sand, during the production of fluid from a subterranean formation penetrated by a well bore is a continuing problem. The transported particulate solids can erode or cause significant wear in the production equipment used in the fluid production process. The particulates also can clog or plug the well bore thereby limiting or completely stopping fluid production. Further, the transported particulates may need to be separated from the produced fluid adding further expense to the processing.
The particulates that are transported during production of fluid may be present for various reasons. In some cases, the particulates are naturally occurring, for example, due to an unconsolidated or weakly consolidated nature of a subterranean formation. In other cases, the particulates can be present as a result of well treatments placing particulates in a well bore or formation, such as in gravel packing or fracturing operations. Gravel packing in a well may include the use of gravel, sand, or both, and the gravel often includes some sand. In the treatment of subterranean formations, it is common to place particulate materials, such as sand, as a filter medium and/or as a proppant in the near well bore area and in fractures extending outwardly from the well bore.
For example, in fracturing operations, proppant is carried into fractures created when hydraulic pressure is applied to these subterranean rock formations to a point where fractures are developed. Proppant suspended in a viscosified fracturing fluid is carried outwardly away from the well bore within the fractures as they are created and extended with continued pumping. Upon release of pumping pressure, the proppant materials remain in the fractures holding the separated rock faces in an open position forming a channel for flow of formation fluids back to the well bore.
Proppant flowback is the transport of proppant material back into the well bore with the production of formation fluids following fracturing. This undesirable result causes problems such as undue wear on production equipment and the need for separation of solids from the produced fluid. Proppant flowback occasionally also decreases the efficiency of the fracturing operation because the proppant does not remain within the fracture and may limit the width or conductivity of the created flow channel.
Current techniques for controlling the flowback of proppant include coating the particulate with curable resin, or blending the particulate material with fibrous materials, tackifying agents, or deformable particulates. E.g., U.S. Pat. No. 6,328,105 to Betzold, U.S. Pat. No. 6,172,011 to Card et al., and U.S. Pat. No. 6,047,772 to Weaver et al.
For a multi-zone well that has been fractured with proppant and is plagued with proppant flowback problems, it is quite difficult to identify the zone from which the proppant is emanating unless the proppant is tagged with a tracer.
Radioactive materials have been commonly used in the logging or tagging of sand or proppant placement, however, such techniques do not address particulate that may have been previously placed in operations such as gravel packing or fracturing. Further, such radioactive materials are hazardous to the environment and the techniques for utilizing such radioactive materials are complex, expensive, and time consuming.
Sometimes, particulates produced during fluid production can have multiples sources from different zones of a wellbore and for different causes.
Particulate production from a wellbore can be a normal, expected, and predictable process. At times, however, it may be different from the normal or expected. This can be indicative of a geomechanical failure in a zone at or near the wellbore.
It is possible to easily measure at the surface particulate production, which measurements can be evaluated as being normal or abnormal. More difficult is to directly relate the sand production to particular zones or locations. In many well architecture and completion approaches, for example, in multiple zone completions, long completion zones, deviated or horizontal wellbores, and multilateral completions, being able to do so would be particularly valuable. There are also multi-well developments including off-shore scenarios wherein production from two or more wells may be combined (e.g. at a sub-sea manifold), and the combined production flow may include particulate production from one or the other well.
Being able to easily localize the source of particulate production would drive better focus on decisions for remediation actions to take (or not take), such as whether and where to clean-out, adjust production rates, cement, plug, open or close windows, abandon a wellbore, etc. Therefore, there is a need for methods for localizing the source of particulate production in subterranean wells to avoid the above problems.
U.S. Pat. No. 6,725,926 issued Apr. 27, 2004, having for named inventors Philip D. Nguyen, Jimmie D. Weaver, and Johnny A. Barton, filed on Nov. 18, 2002, discloses as described in the abstract thereof compositions and methods for determining the source of treatment fluids being produced from a production formation having multiple zones by introducing a treatment composition having a tracking material into a zone in the subterranean formation, and detecting the tracking material in the treatment composition so that if flows back from the subterranean formation. The entirety of U.S. Pat. No. 6,725,926 is incorporated herein by reference.